کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5205150 | 1381987 | 2007 | 7 صفحه PDF | دانلود رایگان |
Highly stereoregular polymerization of 2-ethynyl-3-n-octylthiophene was successfully performed with a [Rh(norbornadiene)Cl]2 catalyst to produce the corresponding polymers in fairly high yields by using triethylamine or a mixture of it with other solvents as the polymerization solvent. We found that the obtained polymer using CHCl3 was a mixture of cis-transoid form, ca. 68% and trans-transoid form, ca. 32% unlike our previous conjecture. Further, we found that the cis-to-trans isomerization can be also induced when the pristine predominant cis polymer was subjected to mechanochemical grinding (MCG) treatment at 77Â K using a mortar filled with liquid nitrogen to decrease the cis content from ca. 68% to ca. 7%. The polymers obtained before and after the MCG treatment were characterized in detail using 1H NMR, laser Raman, solution UV-vis, diffuse reflective UV-vis, and ESR methods in order to determine the geometry of the main-chain CC bonds in the polymer. The data showed that the polymer obtained by the treatment has a fairly distorted trans conjugation length, i.e., bent trans structure in which less mobile unpaired electrons generated by the rotational scission of the original cis CC bonds are stabilized.
Journal: Polymer Degradation and Stability - Volume 92, Issue 2, February 2007, Pages 253-259